How to figure out if Ineed to upgrade my electrical panel

[Ignoramus25700]

Ihave a 200 amp electrical panel. I am thinking about upgrading my hot tub/spa, by replacing the old guts of it with a new control center and new heater, pump, etc etc. The only thing that will remain is shell and plumbing.

My current equipment is 110v based and I want to put in 220v equipment. Obviously it will run higher amps due to the much more powerful heater.

My question is, how do I know if my panel is adequate and that I do not exceed the amp limitations? What is the relevant part of the NEC that Ishould study?

thanks.

i

[gabriel]

Ain;t the max for residential 200A? For what it's worth, I've been running

100A with a spa as well without problems.

Anyway, there's some limit as to how much you can potentially overload (ie, if you ran around and turned every circuit on at peak capacity), but I do not know it. Maybe someone else does. I would not worry about it.

[Ignoramus25700]

The only two other high current appliances that I have at home is electric kitchen range/stove, and A/C. It is also 220v based. The rest is usual bullshit, lighting, furnace, various TVs etc.

I guess I could add up the amp rating of the stove circuit breaker, the A/C circuit breaker, the proposed hot tub, and then add 30 amps of fudge factor. Would that be a very invalid approach?

Wild guesses:

Stove 30A A/C 50A Hot Tub 50A Fudge 30A ======= ==== Total 160A

Since this 160A total is comfortably below 200A, I can safely add a 50A hot tub, right?

i

[gabriel]

I would certainly think so... Again, there are some rules/laws about this, but you should be fine.

If you overload the whole thing the main breaker will trip, right?

[Tom Horne]

Gabriel In US practice there is no Maximum for a home and I have worked on homes that had four hundred ampere services.

-- Tom H

[gabriel]

Then I stand corrected. I was under that impression sbecause the electrician who installed a sub-panel for me said somethign to that effect...

[Tom Horne]

Except in Min/Max states there is a possibility of some local amendment containing such a limitation.

-- Tom

[Joseph Meehan]

It can have a 50% increase in capacity and will only need 75% of the current equipment.

[Ignoramus25700]

I am sorry, I do not understand what you are saying.

i

[zxcvbob]

A 200A panel should be fine, unless it's a Federal Pacific.

HTH :-)

Bob

[HA HA Budys Here]

Are you kidding? A 60a Federal breaker will hold the entire load just fine ;-)

[Joseph Meehan]

If you use 50 amps at 110V and the new system is 50% higher demand (75 amps at 110V) and you switch to 220V that 75 amps drops to 37.5 amps.

37.5 amps at 220v = 8250 watts 75.0 amps at 110v = 8250 watts.

[Ignoramus25700]

The way hot tub heaters work is that they are resistors with a given resistance. So, if they produce X amps at 110 volts, they would produce 2X amps at 220 volts, due to Ohm's law.

A typical 220v hot tub heater is about 10 kilowatts. Or about 45 amps.

i

[Mike O.]

Actually, 220v equipment is typically lower amperage. Power level (watts) is volts * amps, so at a given level if you double the volts, you halve the amps. One advantage of 220v equipment is that you can use smaller wires, or get less voltage drop on the same size wires as used in 110 circuits.

Also, in your other post you listed the current loads of some of your appliances. Those are going to be peak loads and not constant, and probably have a safety margin built in. The "fudge" (fridge?) is only going to hit it's max for a second or two at startup, and probably isn't going to pull

30A even then. Your stove's not going to be using 30A, unless you're running all the burners and oven on high at the same time..

There's web sites around that have info on calculating your load, but 200A is probably enough unless you have a bunch of high power stuff (welder, etc.)

Just my $1.23 (2 cents adjusted for inflation...)

Mike O.

[Ignoramus25700]

except for spa heaters.

fudge is a shorthand for "fudge factor". Let's someone is vacuuming the floor and another persin is using a circular saw while the stove and spa are using electricity.

which could happen, right?

That's my hunch as well, but I want to confirm it.

i

[Mark or Sue]

From the equipment you've listed, I think you have plenty of power. A 200A service can meet just about anyone's needs unless they have a mansion or electric heat. If your hot tub is 50A now (at

120V), I don't believe it will be much more later. I've never seen a hot tub that required anything larger than a 60A double pole (240V) breaker, although I'm sure they exist.

You can go here to learn how to do a full up load calculation, but it is rather complicated. Greg posted the easier method, but even it confuses people.

-- Mark Kent, WA

[Childfree Scott]

How old is the existing electrical panel? If it's old enough it might be worth upgrading because 40 year old breakers aren't particularly reliable anyway.

[Ignoramus31599]

No, it is 20A. Very low power heater. That's why I want a powerful 220v heater.

Remember though, 50A 220v is more load on the panel than 50A 110v.

Just what I was looking for, thanks.

i

[Ignoramus31599]

23 years old. i

[zxcvbob]

Not really. 50A 220V is a balanced load. 50A 110V is unbalanced, and it depends on what offsets it on the other phase (phase is not really the right terminology. "Leg" perhaps? Or "tap"?).

I don't think I've ever seen a 50A one-pole breaker.

Best regards, Bob